Comparison of Exclusive Reactions at Large $T$

Baller, B.R. ; Blazey, G.C. ; Courant, H. ; et al.
Phys.Rev.Lett. 60 (1988) 1118-1121, 1988.
Inspire Record 264273 DOI 10.17182/hepdata.3063

Cross sections or upper limits are reported for 12 meson-baryon and two baryon-baryon reactions for an incident momentum of 9.9 GeV/c, near 90° c.m.: π±p→pπ±,pp±,π+°±,K+Σ±, (Λ0/Σ0)K0; K±p→pK±; p±p→pp. By studying the flavor dependence of the different reactions, we have been able to isolate the quark-interchange mechanism as dominant over gluon exchange and quark-antiquark annihilation.

2 data tables

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Comparison of 20 exclusive reactions at large t

White, C. ; Appel, R. ; Barton, D.S. ; et al.
Phys.Rev.D 49 (1994) 58-78, 1994.
Inspire Record 377535 DOI 10.17182/hepdata.50306

We report a study of 20 exclusive reactions measured at the AGS at 5.9 GeV/c incident momentum, 90° center of mass. This experiment confirms the strong quark flow dependence of two-body hadron-hadron scattering at large angle. At 9.9 GeV/c an upper limit had been set for the ratio of cross sections for (p¯p→p¯p)(pp→pp) at 90° c.m., with the ratio less than 4%. The present experiment was performed at lower energy to gain sensitivity, but was still within the fixed angle scaling region. A ratio R(p¯ppp)≈140 was measured at 5.9 GeV/c, 90° c.m. in comparison to a ratio near 1.7 for small angle scattering. In addition, many other reactions were measured, often for the first time at 90° c.m. in the scaling region, using beams of π±, K±, p, and p¯ on a hydrogen target. There are similar large differences in cross sections for other reactions: R(K−p→π+Σ−K−p→π−Σ+)≈112, for example. The relative magnitudes of the different cross sections are consistent with the dominance of quark interchange in these 90° reactions, and indicate that pure gluon exchange and quark-antiquark annihilation diagrams are much less important. The angular dependence of several elastic cross sections and the energy dependence at a fixed angle of many of the reactions are also presented.

21 data tables

Cross sections at 90 degrees in the centre-of-mass.

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Total cross-sections for pi- p ---> lambda k0 from threshold to 1.13 gev/c

Jones, J.J. ; Bowen, T. ; Dawes, W.R. ; et al.
Phys.Rev.Lett. 26 (1971) 860-863, 1971.
Inspire Record 69027 DOI 10.17182/hepdata.21505

Total cross sections for π−p→ΛK0 have been measured using optical spark chambers from threshold to 1.13−GeVc beam momentum in 19−MeVc intervals, but with a 1−MeVc resolution in the regions of the ΛK and ΣK thresholds. The behavior near ΛK threshold indicates a significant s-wave contribution, but this experiment is unable to resolve any cusplike behavior in the region of the ΣK thresholds. The cross section shows a broad peak in the vicinity of 1.05−GeVc beam momentum.

1 data table

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High Statistics Measurement of Polarization in $\pi^- p \to K^0 \Lambda$ at 3-{GeV}/$c$ and 5-{GeV}/$c$

Snyder, A. ; Ambats, I. ; Meyer, W.T. ; et al.
Phys.Rev.D 21 (1980) 599, 1980.
Inspire Record 8072 DOI 10.17182/hepdata.24173

We have measured the polarization of the Λ hyperon produced in the reaction π−p→K0Λ at 3 and 5 GeV/c, for four-momentum transfers t′ out to 1.6 GeV2, by observing the parity-violating decay Λ→pπ−. With an increase in statistical power by a factor of 3 to 4 over the best previous experiments in this energy range, we confirm earlier observations that the polarization is small and positive below t′=0.4 GeV2, becoming large and positive for larger values of t′. In particular, at 5 GeV/c for all t′ between 0.8 and 1.6 GeV2 the polarization is consistent with a value of - 1.

2 data tables

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Cross-Sections and Polarizations in the Reactions pi- p --> Lambda K0 and pi- p --> Lambda K* (890) Near the Backward Direction, from 3-GeV/c to 6-GeV/c

Ward, C.E.W. ; Ambats, I. ; Lesnik, A. ; et al.
Phys.Rev.D 16 (1977) 2041, 1977.
Inspire Record 4930 DOI 10.17182/hepdata.24506

We have measured the differential cross sections and Λ polarizations in the reactions π−p→ΛK0 and π−p→ΛK*0 (890) near the backward direction, at 3, 4, 5, and 6 GeV/c. Data equal to several times the world's total sample above 2 GeV/c were recorded. Both reactions are characterized by cross sections falling rapidly with beam momentum, and by large positive Λ polarizations for u′ between 0.0 and 0.6 GeV2. Analysis of π−p→ΛK0 yields an effective Regge trajectory consistent with antishrinkage of the backward peak. Separation into amplitudes of definite-parity-naturality exchange shows the reaction to be dominated by unnatural-parity exchange. The energy behavior of this exchange is, however, not consistent with a single linear baryon Regge trajectory or exchange-degenerate pair of trajectories. An apparent normalization discrepancy between data on π−p→ΛK0 of a CERN-ETH group and other high-statistics data including that of this experiment is discussed.

10 data tables

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